When a person experiences sudden cardiac arrest, the heart’s electrical system malfunctions, causing it to stop beating effectively. Cardiopulmonary Resuscitation (CPR) manually circulates oxygenated blood to the brain and other organs until the heart’s rhythm can be restored. The arrival of an Automated External Defibrillator (AED) allows for the delivery of an electrical shock to reset the heart. Combining immediate, high-quality CPR with rapid defibrillation significantly increases the chances of survival. Survival chances decrease by about 7 to 10 percent every minute without intervention, making the integration of these techniques essential.
Preparing the Patient and Applying the AED Pads
The priority upon the AED’s arrival is to minimize the interruption of chest compressions while preparing the device for use. The rescuer performing compressions should continue without pause while a second rescuer immediately powers on the AED, which provides voice prompts. The patient’s chest must be quickly exposed by removing or cutting away clothing to ensure the AED pads adhere properly and the electrical current can pass through. If the chest is wet, it must be wiped dry. Excessive chest hair may need to be quickly shaved if available, as moisture and hair can interfere with pad contact.
The AED pads must be applied directly to the bare skin in the correct positions, following the diagrams shown on the pads themselves. For an adult, one pad is placed on the upper right side of the chest, above the nipple and to the right of the breastbone. The second pad is positioned on the lower left side of the chest, slightly below the armpit and on the rib cage. Applying the pads quickly should be performed while chest compressions continue, as any break in compressions can cause a drop in blood pressure. Once the pads are securely placed, the rescuer should plug the pad connector cable into the AED unit, aiming to keep the pause in compressions under ten seconds.
Analyzing the Rhythm and Delivering the Shock
After the pads are connected, the AED will prompt rescuers to pause CPR so it can analyze the heart’s electrical rhythm. The rescuer performing compressions must stop, and everyone must ensure they are not touching the patient or any connected equipment. Rescuers must loudly and clearly announce “Clear!” before the AED begins its analysis to confirm everyone’s safety. The AED recognizes specific life-threatening rhythms, primarily ventricular fibrillation and pulseless ventricular tachycardia, which require an electrical shock.
If the AED determines the patient is in a shockable rhythm, it will advise a shock and begin charging its internal capacitor. A rescuer must again ensure no one is touching the patient and loudly announce “Clear!” before pressing the shock button on a semi-automatic AED. For a fully-automatic device, the rescuer stands clear while the device delivers the shock. The electrical discharge briefly stops all electrical activity in the heart, allowing the heart’s natural pacemaker to potentially resume a normal rhythm. If the AED says “No Shock Advised,” the rhythm cannot be treated by defibrillation, and the rescuer must immediately move to the next phase of the resuscitation sequence.
Immediate Steps Following AED Use
The moment the shock is delivered, or the AED announces “No Shock Advised,” the rescuer must immediately resume chest compressions without delay. Guidelines mandate two minutes of high-quality CPR following any analysis or shock, as circulating blood flow is necessary for the heart to recover. The AED often provides a metronome or voice prompt to help maintain the correct compression rate, typically between 100 and 120 compressions per minute.
If multiple rescuers are present, they should switch the person performing chest compressions every two minutes to prevent fatigue, which reduces the quality and depth of compressions. Throughout this two-minute cycle, the AED pads must remain attached to the patient, and the AED should not be turned off. The device monitors the patient’s condition and automatically prompts a new rhythm analysis at the end of the two-minute CPR period. Rescuers should continue to follow the AED’s voice prompts and repeat the cycle of CPR, analysis, and shock until emergency medical services arrive or the patient becomes responsive.